Telephone system



Feb. 15, 1927;

B. A. WALLACE- TELEPHONE SYSTEM Filed Dec. 1922 r l ll lS', and more 'pattic'ularly to that 'sysihg;

f e-11- tnte'e re'h1ployecl for ihterconheeting; subecnhers telephonellnes 1n conversatlonal Patented Feb. 15, 1927.

'" BERT A. WALLACE, oF'e IcAeQ, ILLINOISQ SSIGNQR To KEL O G'SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPO'RA'TI'ON 01 ILLINOIS.

* TELEPHCim ey ei izm.

" My invention relates to telephone sys-l item wherein manuallyoperated cord or link cult.

' for i litercofineeting 'cfnmho battery tele-' inoh h-zittery telephene lines 'a nd magneto telephone lines. 1 "Aiibther' feiltu 'e o f my 'mventlen 1s the bp'erator is" prex e'n tecl fronil'is'tenihg in on a 'cbliihienhaittery telepho ne line I Still ziiiQtherfeatureof my invention is 'Itentibn I" the: same lepefator who answerecl] u 'm-gaming 111 "be hacl to" the eeeenipanyingdrawing.

Referring jnow' in general te the "drawing, I show a commqn' battery calhng substation,

feathre of my inventien'is the pirovieion cord or link UH'C-Ultwhich maybe used'] 15 'iil giiflSibh of means whreby'fth'e exchangeYlinesfis ploviicled "With'efi' elnsweliing Dlug "AP'amla'calhng'plug will i engaging a 10k las pointed gout listenlhg key LK is blfovfdedjjfor eenneeting cut-eff {relays ,CO and CO; Ihhltip'le jaeks lhml J; ahcllthe multiple linelamp sig-j Ito Pr 'S will be 'iqo'intecl fen.

le fsecr et service, 1 between: I eubconductors of the ercl C, 43ml Jis 5 miles ailcl S. 1 The jackef the line'ire disto Tcdntrol the eperhtiqnfof the ,bpered tors '50? t. th 'ope'z aters vposi'tijn is 'lighteclg and tions; anclthere isr a line Signal for each jag-k7 ut the op e mtol s "posit-ion so that when a i call is initiated b'v el"v the line; the line signal ine of aph u z lity of o'pel ator s" may seize the"? call to the ez zcluslen of the other ope-raters.v

. 'i l a r ii z w e li s i. st zitio'n D and a local battery or magneto al.1188311, 5 will be latel po nted on ren l 1110!?6 bar has answered, in case the calling subscriber replaces his receiver upon the switchhookafter informing the operator or l11S wants. The calhngend of the cord C is provided ,with a sleeve relay SR which energizes 7 when thecalling plug CP is inserted into one of the multiple jacks J provided a plug AP or CP of another cord circuit is not already engaging one'of the jacks J The relay SR will not, however, operate when theplug CP is inserted into, a jack LJ '01? a magneto line, as the sleeve of the jack LJ is free from ground. A calling supervisory relay -CR is provided "for controlling the operationof the supervisory signal CL; A

, relay RR is provided for also controlling thejOpBI'dlllOn of the operators disconnect rela ODR, and also for effecting operation of t e supervisory signal CL, when the plug CP is connected to a jack of a magneto line to indicate a disconnection and to also llldl",

' j cate a recall, which will be fully described 'nect :ringin'g current; to the called sub-' later; I a A ringing control relay RCR is provided,

fwhich energizes when the operator depresses fullyrth e ringingkey ,RK, to bring about the energiz ation of an interrupter relay IR, and to also connect'an interrupter device I in circuit with the lower winding of the interrupter relay, whereby said relay IR is caused to be intermittently operatedto conscribers line from one'of the ringing frequency, generators G, G, G and G I The signal CL lights as soon as the calling plug CP" is inserted into the jackJ, and remains lighted until the operator depresses the fringing key RK; the burning lamp CL thus 1 servinglat this time as a signal to notify the operator that ringing current has not been connected to vthe calledliner The lamp CL also serves to notify the operator when the called subscriber has replaced his receiver i: upon its switchhook.

'45 LJ, relay SR fails to energize, and in this 'Wh'en'th'e plug or is inserted into ack case ringing current. will only be applied to the called lineso long as the ringing key common battery subscriberstelephOnelineS, ,Assumiin'g th tthe subscriber at substation A terminating in jack LJ,

RK isl in'its fully depressed position, as there 'will be no locking circuit provided for maintaining the ringing control relay RCR energized to close a circuit for relay IR, when the key RK is not in its fully depressed posit-ion. In this instance, the operator willdepre'ss fully'key RK each time ringing current is applied to the called line 'I Referrin'gnow more in detail to the opera tiong otmy invention, '1' will first describethe operation of my cord in interconnecting 'desires to converse with the subscriber at 'substatlon 13, he -Wlll remove his receiver irom' its. switchhook, thus closing a circuit ground.

cut-off relay for the line relay LR, traced from battery,

through the winding of said relay Lt,

tions. Assuming that the operator at cord circuit C is the first one to answer the call,

the insertion of the answering plug AP, into the jack J of the calling line establishes a series energizing circuit for the cut-off relay C0 of the line circuit L and the sleeve relay SR, the circuit being traced from battery,

through the low resistance winding 6'and high resistance winding ,7 of said relay SR, conductor 8, sleeve contacts of plug AP and jack J to ground through the winding of CO. The closure of alternate contact 9 of relay SR shunts out the high resistance winding 7 and closes a low resist ance circuit for relay SR, traced'from battery through the low resistance winding 6 and alternate contact 9 of relay SR, and

over the previously traced circuit. l The cut- V 0a relay CO in the line circuit L energized in series with relay SR over the first circuit traced and will be maintained energized over the last traced circuit so long as the" plug AP remains in the answering jack J, thereby taking line relay 'LR from under the control or the subscriber at substation A. Relay SR upon. energizing closes a circuit for the answering supervisory relay,v AR,

traced from battery through the lower wind ing of said relay AR,alternate contact 10 of relay SR, windingc of repeating coil normal contact 11 of key RB, ring contacts of plug AP and jack J, through the alternate closed switchhook contacts of substation A, tip contactsv'o't' jack J and plug AP, normal contact 12 of key RB, winding a of repeating coil RC, alternate'contact 13 of relay SE, to ground through the upper .winding of relay AR; Relay'AR energizing opens its normally closed contact M to prevent the premature lighting of thesupervisory lamp AS. H

The operator at cord circuit C having inserted the plug AP into the multiple jack J,

and will theninquirethelwants of the calling subscriber at substation A.

The operators T willoperate the listening key LK to connect her telephone setC to the cord circuit C,

setO'is connected to the cord 'C- overrthe i ollowing circuit, point l5 otthe tip conductor of said cord, conductor '16, alternate contact 17 of listening key LK, normal contact 1 8 of relay ODR, receiver 01' operators with the calling subsci'ibcrs line even thoughrepeating coil RC, tip conductor normal conshe doesoperate her listening key. Thus "secret SGLY'lCG is provided between'the operator at cord an'd'the subscriber at Substation A, which is effected in ,this'inanner: The relay SR oi thecord at these'cond operatofs position will not energize in this instance, due to the shunt plat-ed about the high resistance winding 7 of relay SR lot the second ope'rators cord circuit C by the low resistance circuit of the relay SE of the first operators cord. and this low resistance circuit will shunt the-low and high resistance windings of the relay- SE of the second operators' cord circuit -to render thesame inoperative as long as the plug; AP ot' .the cord C remains in the jack J. The role SR of the second'o'perators cord circuit failing to energize, a circuit will be closed for the relay RR of the second operators cord 'ircfuit, traced from the battery potential on the ringcontact'of the multiple jack. whii-h sleeve of the multiple ack J and should is in multiple circuit with the answering,

'jack J of thejcalliin line, ring contact of the answering plug of the second operatofis cord-c rcuit, normal contact 11 of key RB, ring conductor and winding 0 of the repeatcoil RC of the second cord circuit windinc; of relay RR, normal contact 13 of relay SR, ot the second cord, winding 64 of the tact 12 of key RB'and tip contact of the answering plug: of the said second operator s cord circuit, and to ground at the tip contact of the said multiple jack which is in multiple circuit with the answering ]21Cl J of the calling line. Relay RR of the second operators cord circuit energiZing:v over 'ths circuit will close'its alternate contacts,

which will provide an'ener izi'ng circuit for the second op'crato'rs disconnect relay )D-R associated with said second-operatoi-ls cord circuit, when the second operator operates her listening key to connect liertelephone set in circuit to permit llGliO converse with -the calling subscriber at substation. A, the

circuit forsaid relay ODR of the second cord circuit being traced from battery through the winding of relay- ODR,-normal contact 23' of listening key LK, conductors 24v and closed contacts 18 and 19-,"therebyidiscon meeting" the second operators telephone set from her cord circuit connected to the calling subscribers line, which will prev-ent tl ie second operator from conversing-with the callinn; subscriber at substation A. The second operator failing to receive a response upon inquiring the \Y aIliZS Of the call-inn subscriber, will know that the call hasbeen scized by another operator,- and willdisconnect her- 75 cord circuit fron'i the multiple jack of the calling line, whereupon the said relays-RR and ODR of the second operators cord circuit will restore to normal.

Thus, from the foregoing described opera 180-.

lion; it is at once apparcntthat an operator attempting to answer'a call afteutliecallf has been seized by another o )erator, will be prevented from establishing an operative connection between her telephoiieset and the {3'85 ca'llin'g line due to't'he operationof relays RR and ODR' of the cord circuit of the'said operator attempting to answer the call-subsequently to another operator. 7

Revertingnow to when. the opei ator8atthe cord circuit C inquires the wants of the calling subscriber at substation A, and as it has been assumed that the 'subscriber atsubstation B is wanted, the operator will make the usual test to determine the idle or busy condition of the called line by touching the tip of the callingplug GP to the .the callingsubscriber of the busy: condition of the called line, and will: ltlien'withdraw the plug AP from the jack J, whereupon the cord C restores to normal. Assuming,

however,. that. the; called line is idle, the

operatoi will fail to receive a click in lierello ear, and will insert the calling plug GP into the jack J, of the called-line. -Upon the insertion 0t. tlieplug GP into the-jack J, an energizing circuit isclosed forthe sleeve relay SR as follows: battery, through; the upper low resistance winding 28 and lower high 1GS1SlLaI1CG;W1IlCllI1,9 29, conductor 30,

sleeve contacts of plug CP and jack J to ground through the winding of cut-ollhrclay CO.. Relay CO energizes overthis eir- 1, 0 cuit to takeythe line'i'elay'LR" tronrthe control of the calledsubscriber at substation B, and relay ESR energizing over this circuit closes'its alternatecontact :81, thereby shunting out its loweivhigh resisance wind-' ing 29 andesablishes-aloW IQSiStEJLCG'ClI .cu'it toritselt, traced j'frombattery,through I the upper low resistance winding-28- ot'said relay SR, alternate contact 31' of relay SB,

and over, the previouslytraced circuit. yThe T i contact 36ofrelay AR, alternatecontact 37 calling supervisory lamp signal. CL will light and continue to burn until-the operator depresses a plunger of the ringing key Rh to connect'ringing current to the called line, the "circuit for said lamp signal being traced from battery, through the said lamp CL, 7 normal contact'32 of the-ringing control re- 1 lay RCR, alternate contact 33 of relay SR,-

3 {normal contact 34 ofthe calling supervisory V applied'to thecalled subscribers line.

operator will now 7' '15 plungers of the ringing key RK to connect relay CR to ground. The lighting of lamp CL in this instance serves to indicate to the operator that ringing current has not been The depress the proper ringing "frequency generator in circuitto apply ringingv current to the called subscribers line, and assuming that gen- 7 'erator G is of the proper trequency to wl11ch the. call bell at the called substationB isrcsponsive, the operator depressing the plunger of "the rlnglng kcy- RK corresponding to generator G to its fully depressed position, a circult Vlll be closed for the ring- 1ngcontrol relay RCR, which may be traced c from'batterylthrough the winding of said relay RC'R, conductor 35, alternate contact 7 36 of relay AR, alternate contact 37 of relay SR, conductor 38, alternate end spring contact 39 of ringing key BK, when the said Y )lun 'er of rin 'in ke j RK is inits fully b be 2D 7 t.

depressed position, conductor-'40, to ground .a locking circuit for itself through its alternate contact 32, said locking circuit being traced from battery, through the winding ofsaid relay RCR, conductor 35, alternate of relay SR, conductor 38, alternate coni is closed for theinterrupter relay IR to cause said relay IR to energize to connect the :7 -jgeneratorG in circuit with the called line tact 32 of relay RCR, conductor 42, alternate contact 33 of relay SE to ground through normal contact 34 of relay CR.

\Vhen the'plunger of the key RK is fully depressed and'relay RCR energizes, a circuit even though a non-conducting segment of #the constantly rotating interrupter device I is in circuit with the lower Winding of said relay IR, wvhereby ringing current is instantaneously applied to th'e'called line when the-plunger key BK is fully depressed and relay RGR operates. The circuit for .said relay IR may be traced from battery, through the upper winding of the relay IR,

alternatecontact 43of relay RGR to ground through the'alternate end spring contact 44 '7 'of the ringing keyRK. Relay IR will remain energized over this circuit soilong as the plungerf'is in its fully depresed position to close alternate'contact 44, and the onev of the of relay ROE to ground through a conducting segment of the constantly rotating interrupter device I. lVhen alternate contact 44 of key BK is opened, relay IR will bein- ,termittently energized and de-energized over the last'traced circuit to lnterm ttently ap-- ply ringing current to thecalled line to operate the callbell at substation B.

The circuit for the ringing current may be traced as follows: from ground, through the frequencyv generator G, alternate closed contact 52 and normal contact 53 of the,v

ringing key BK, conductor 54, alternate call bell at substation B, ring contacts of jack J and plug GP, to ground through alternate contact 48 of relayIR. A revertive ringing tone is also communicated to the calling subscriber to apprise him of the fact that the called for subscriber is being signaled, the circuit for this revertive ringing tone being from ground through the generator G conductor 55 alternate contact 56 of relay IR, Winding b of the repeating coil RC, alternate'contact'50 ofxrelay SE to ground through the upper winding of relay CR, whereupon the said revertive ringing tone will be induced into the winding a of the repeating coil RC and then transmitted through the calling substation A; Should the subscriber at the substation A replace his receiver upon itsswitchhook before the called-for subscriber at substation call bell, the further application ofringing current to the called linewill be automat ically discontinued, due to the fact that the supervisory relay AR which'is controlled by n V the calling subscriber at substation A will de-energizewhen the calling subscriber replaces his receiver, and relay AR, restoring to normal, opens its alternate contact 36,.

thereby opening thelocking circuit of relay RCR to cause the same to restore, which in I restoring opens the circuit through the low er winding of the interrupter relay IR whereupon the relay IR immediately restores .to its normal position to prevent the further application of ringing current to the called line. the calling subscriber'at Adoes not replace his receiver before the called-for subscriber responds, after. the removal of the receiver at substation B, and when relay IR is. in deenergized position, as will be the caserduring a non-ringingperiod, a circuit willbe closed for the calling supervisory relay CR,

Assuming, however, that traced from battery, through the lower winding ofithe relay CR, alternate contact 47 of relay SR, windingd of the repeating coil RC, alternate contact 50 or relaySR,

coil RC, normal contact 48 of relay ring'contacts of plug CP and jack J through the now" closed alternate switch hook contacts of the substation'B, tip con:

tacts of jack J "and plug GP, normal contact 4901 relay IR, winding 6 of repeating to ground through the upper Winding of re lay CR. Relay CR 'Will energize over this 1 circuit and Will open its normally closedv contact 34, thereby opening the locking circuit of the ringing control relay RCR,

whereupon said relay RCR Willrestore, as

pointed out above," to prevent another en ergization of relay lR, whereby further ap-" plication of ringing current to the called subscrib'ers line is prevented, V

The subscribers atsubstations A and 'B are-now in conversational circuit, which may "be traced over the heavily marked conduc-J tors; Should the operator at cordcircuit C attempt to listen in on the conversation by operating her listening keyBK, she is prevented from doing so bythe operation of the relayfODli',-' which will energize to; open its normally closed contacts 18 and 19.

The circuit for said' relay ODR may be traced from battery,"throughfthe Winding of therelay ODE, alternate contact 23 of the flistening key LK, con'duct0r '24, alternate] contact 58 of relay 'GR, conductor 59, alternate contact 60 of listening hey LK,talternate contact 14' of relay to ground. .Thus,

it isclear that the operator cannotc'onnect 5 her-telephone set circuit so as to listen in on'the conversation between the subscribers at substations A and B. In case the subscriber at Substation A replaces his receiverupon its fsvvitchhook, supervisory relay AR will restore andopen its alternate contact 14, thereby opening the circuit of re lay'ODR at alternate contact 14; Should he operator now .operate' her listening key LK,-her"teleph'one setO Will be connected to the cord 6, which will enable theoperator to communicate with the subscriber at sub station B, providedsaidsubscriber has notreplaced his receiver upon its switchho'ok;

Inj'case the subscriber at substation B replaces his receiver upon its switchhook, su-" pervisory-relay OR will restore and open its'alternate contact 34, thereby openingthe circuit of the relay ODR, The operator inay'nowoperate her listening key LK Without causing the energiz'ation ofrelay ODE,

and connect her telephone set 'Of'to the cord, circuit C, which will enable her to converse" with the subscriber at substation A, providing said subscriber at A has not replaced his i I receiver upon its switchhook. 7 Thus, it is clear that the operator will only be-ab'le to;

connect her telephone set 0 to the cord circuit C When one'orboth of the subscribers at A and B has or haye replaced the receiver upon its switchhook, but cannot connect said telephone set 0 to the'cord When both the calling and calledsubscribers-have their receivers off their respective sivitchhooks;

Assumlng nowthat conversation. has terminated,and th'esubscribers at A a'nd'B have battery through the said lamp AS, alternate contact 60 of relay SE, to ground through normal contact 140i relay AR, and the circuit for the lamp CL being from battery i through the said lamp CL,'norrn alcontaet 32 of relay RCR, conductor 42, alternate contact 3 3 of relay SR to ground through normal contact 34 of relay CR. v The supervisory lamps AS and GS will light over these circuits, and the operator observing them,

will know that conversation has terminated and Will withdraw theplugs Al? and C? from the jacks J and J, respectively, Where- 11 on the cord circuit C restores to normal and the cut-off relays CD and CO, restore to normal. 1 I I It sometimes occurs that after, the calling subscriber has stated liis Wants-"to the exchange operator, hereplaces 'hi'srreceiverf upon its switchhook and awaits a call from the operator when she hasthe called-ior subscriber on the line, and theoperator signal back the calling subscriber :byf oper-f ating a rin'gback key RB WlllCllNVlll close.

its alternate contactsfll and 12 ,tofconnect subscribers line to signal the calling sub scriber.

Reverting noiv to Iivhen the I operator at cord C tested to determine the clleor busy,

the ringing generator HG to the said calling condition of the called line B,fand assumingthat saidcallechfor line is *found busy, but 1 tion and inserts the calling plug CPinto the jack J .7 and even though the-listening key LK is in itsoperatecl position, the operator at, cord circuit C will be prevented from listening n on the conversation at the caliedsubsbribeias line, due to the fact that relay SRlof' cordC- will not energize since the low and high resistance windings of the relay SR of cord C Will be shunted by the low resistance circuit otfa sleeve relay SR ofanother cord circuit already connected to I another 'jack which is inmultiple circuit Withthe calling jack J, if the called-for line "that the operator disregards its busycondiis busy as a' calling line, and in case the,

calledfor linei s busy as va called lin eQthe low and h gh resistance windings of relay QSR of cord circuit C \villbe shuntedbythe low resistance circuit of a sleeve relay SR of another cord circuit'alreadyl conriected to a jack of 'the calledafor' linc which jack is in ,inultip'le' circuit'ivith the calling jack, J. Relay SR failing to energize, relay RR will energize over a circuit tracedfrom battery-potential present on the ring con{ tact of the jackJ, which battery potential is provided from another cord. circuit al- .ready connected to the calledrforsubscribefis line ring contact of plug C1 normal con- .tact'4c8 of therelayIR, winding d ofre- *peating coilRC, throughthe winding of said relay RR, normal contact 62 of relay RCR, normal contact 50 ofrelay SR, winding 1) of the repeatingcoil RC, normal contact49 of relay IR, tip contact of plug GP,

and to the other side of battery at the tip' Contact of the calling jack J, whichis in multiple circuit with the jack to which the other cord 'ci'rcuit is connected. Relay RR energizing, closes its alternate contacts 63,

thereby closing a circuit. for the operators.

disconnectrelay ODR which will energize andopen its normally closed contacts 18 and 19'to prevent the operator from listening.

" -key LK, conductor '24, to ground through f alternate contacts-63 f relay Thus, it is clear thatI haveprovided means for preventingan. operator a cord circuit from listeningin on'abusy called-for line;

.I-Iavin'g. described :mycord circuit for interconnecting common battery subscribers telephone lines, I will now describe the oper- "at on'of my vcord circuit in in'terconnccting magn'eto'subscriber telephone lines:

1 generator '9 at substation D, 'line. limb 74," normal contactof jack LJ, through the Assum g that theisubscriber at the magneto substationD initiates. a 'call by operatin'gthehandgenerator g at his substation ,D, the drop signal DSwill operate to indicate' to the operator at cord circuit Cthat her attention'is. desired, the. circuit for the drop signal DS being from one side of the winding of said signal DS, normal contact i 76 of jack LJ, line limb 7 7 and to the other 1 side of the generator 9 through the alternatecontact 7 8 of said generator,'which alternatecon'tact/YS will be closed whenthe generator 9 is operating; The operator obthe answering plug serving the operated signal DS will insert AP. of the 'cord G into theanswering jack LJ which'will open nor-v mal contacts 7 5 and 6, and at the same time automatically restore the signal DS tonor-.

mal, and she will then throw her listening .key LKto connect her telephone set tothc cordv C, as described in the foregoing part of this specification: The sleeve relay SR will .not'energize when theplug AP'is connected to the jack LJ of a magneto line',fsince there is no ground connectedto-the sleeve ofsaid :jackLJ, and since relay. SR fails to ener -gize, the supervisory-relay ARwill not energize at this time. .The operator cord will now inquire the wants of the calling subscriber at substation C, and assuming that the subscriber at substation is wanted,

the operator will insert the calling plug C1 of cord G into the jack LJ of the called-for subscribers lineE, whereupon the plug GP opensthe normally closed contacts 75"and 76 of said jack LJ to remove the signal DS from the control of called-for subscriber E.. a The sleeve relay SR will not operate when the plug CP is inserted into the jack LJ, since the sleeve ofsaid jack LJ is free from ground, and as the relay SR fails to energize, no 'circuit'is established. for the supervisory lamp signal CL and the said signal will not burn in this instance betore the ringing key RK is. operated, as was the. case whenthe cord G was connected to a commonbattery telephone line; The operator will now operate one or the plungers of the ringing key RK to apply ringing current to the called-for sub 'scribers line, and assuming that the call Y 1bell at the calledfor substationE is respon- 90 sive toringing currentffrom the-' frequency generator G, the plunger ofqthe fringing key RK correspondingto generator. G will he operated, and when in its fully operated *position, the alternate end spring 1 contacts 39 and 44 ot the ringing key RK will be closed, thereby closing an energizing circuit for the r nging control relay BUR. The circuit forthe ringing control relay 1 RUB is ri-on'i" battery, through the jwinding V of said relay ROB, conductor 35,,Il01111fil contact. 37 of" relay SR, conductor 38, alternate contact39 of the endspring ott key RK, to grou nd, through the normal contact el-of relay CR; Relay RCR energizes over this circuit and closes its alternatecon:

tact 43, whereby a circuit ,is closed for the interrupter relay IR traced frombattery through the upper winding of said. relay IR, alternate contact 43', of relay RCR,

alternate contact 4% of the end spring'of the ringing 'key BK to ground. Therrelays RCR and IR remained energized over the above. traced circuits to applyringing current to the called-for subscribers lineE, so long as the plunger of the ringing key RK is fully operated to. close the alternate end spring contacts 89' and 44 of said ring ingkey RK, but when the operator removes herfinger from the plunger, the same will restore to open the said alternatecontacts 89 and 44:, thereby opening the circuits of i the relays RGB and IR to cause the asnie.

to" restore to prevent the further applica tion of ringing current to the. called-"for. 'subscribers line. -The ringing control relay' RCR is not provided with a" locking' circuit in the present connection, as was the case when the plug CP was connected.

to a jack of a CommonIl-battery line, due

.to its fully operated position.

to thefact that relay SR does not energize to close a locking circuit for said ringing control relay RCR. Since relay RCR does ,not lock up,'it is obvious that the interrupter relay IR will not operate intermittently to apply ringing current to the called-for line, and that it Will be necessary to close the alternate end spring contacts 39 and 44 of the ringing key BK each time ringing current is applied to the called-for subscribers line, that is', eachtnne ringing current 18 applied to the called for subscribers line, the operator must operate the plunger of the ringing key BK The circuit for the ringing current may be traced from ground, through generator G, alternate con tact 53 of ringing key BK, conductor '54, al-

ternate contact 49 of relay IR, tip contacts of "plug GP and jack LJ, call bell and normal contact of substation E, ring contacts of jack LJ. and plug GP, to ground through the alternate contact 48 of relay IR. When the end spring contacts 39 and 44 of the ringing key BK are opened, the relay IR will die-energize first and then relay RCR will de-energize, since it is slow-acting due toits construction, so that/When ringing current ceases to be applied to the called .subscribers line: a circuit Will be closed for the ringing'current stored in the condenser associated with the call bell at the substation E'and also forthe line capacity,

traced from the ringcontacts of jack LJ and plug GP, normal contacts 48 and of relay IR, alternate contact 62 of relay RCR, normal contact 50 of relay SR, Where it is discharged into the repeating coil BC. This circuit just traced provides a. discharging circuit for said stored ringing current to prevent the operation of relay RR When relay RCR restores. A revertive ringing tone is also transmitted to the calling subscriber at substation D to notify him that the :called-for subscriber is being signaled, over The talking circuit for the calling and -called subscribers at substations D and E may be traced over the heavily marked conductors. V v

lVhen conversation has terminated and the subscribers have replaced their receivers upon their respective switchhooks and ring off by operating their hand generators and g, supervisory signals AS and "CL will light to indicate to the operator that con versation has terminated. Assuming that the calling subscriber at substation D has replaced his receiverupo'n its switchhook and operates his hand, generator g, relay RR will energize over a circuit traced from we one side of the generator, gat substation.

I), tip contacts of wjack LJ and p1ugAP,]

normal contact 12 of ringback vkey RB,

winding 0 of repeating coil RC, normal con-r tact 13 o f relaySR, througlrthe,Winding of said relay Eli-,Windingo of RC, normal contact 11 or RB,ring contacts of plug AP and jacklLJ, alternate contact '78 to th'e 'other side ot'the generator g, fRelay RR..

energizing over this circuit closes itse alternate'contacts 85, thereby closing a circuit. for the, supervisory relay,ARg'traced from battery, through the lower Windingol said relay AR, normal contact of relay SR, normal contact86'ot' listening TkeyLK to ground through alternate contact 85Io f relay HR, and relay AR- energizing over. this circuit closes a locking circuit for itself which may be traced over the previously traced circuitup to point,87 and then to ground through alternate contact .14 of said relay AR, anda circuit is also closed for r thesupervi-sory signal AS, traced from battery, through the signal AS, normal contact 7 60 of relay SR, normal contact 85 of relay BR (which relay RR will restore when the hand generator 9 at substation D is no longer operated), alternate contact 14 of relay AR to ground. The lamp- AS Will burn over this circuit to notify the operator atcord C that the calling subscriber has replaced his receiver, and nection no longer desired. I e

The subscriber at substation D upon replacing his receiver 'upon its switchhook will ring off to cause the energization of the relay RR, traced from the hand generator that the cong at substation E, tip contacts ofjackLJ and plug GP, normal contact 49 of relay IR, winding 6 of the repeating coilflliC," normal contact 50 of relay SR". normal contactfiQ of ,relay RCR, through the Winding of relay RR, Winding (Z of RC, normal contact 48 I of relav IR rin contacts or ilu CP and u 7 O l b RR energizing over this circuit, closes an energizing circuit for the supervisory relay GR, traced from battery through the lower Winding of said relay CR, normal contact 47 of relay SR, normal contactx90 of.

the listening key LK, conductor 91, to

ground through alternate contact 63 of relayRR, and relay GR energizing over this circuit will close its alternate contact 34 and lock up to ground through thesaid alternate contact 34 of relay CR, Relay CR jack LJ, alternate: contact 80 and to, the other side of the hand generator Relay energizing also closes a circuit for the calling supervisory signal CL traced from battery through the signal CL, normal contact 32' of relay RCR,-normal contact 33 of relay SR, normal contact 92 of relay RC-R,

normal contact68 of relay RR (relay RR" restoring when generator g ceases operat ing) tofground through alternate contact '34 of relay CR."Thefsupervisory signal CLdig'hts over this circuit to notify the operator that' the subscriber at substation D' has replaced-his receiver upon its switchhook: The operator observing the two burning signals will' operate her listening keyfLKto open its' normally closed contacts'86 and 90 to open the circuits of supervisory relay AR and CR, respectively, to cause said relays-to restore and open'the circuits'of the supervisory signals AS and CL,-and will then restore said key and then withdraw the plugs AP and GP from their respective jacksLJ and LJ, whereupon the system'is restored to its normal position.

Reverting back now to when the subscriber at substation D re/placed his receiver upon its switchhook and operated his hand atorat cord C, he may do so by operating hishand'generator g, to again effect the energiz'ation of relay RR, which will remain energized so long as the generator 9 1s oplerated, andrelay RB energizing will open its normally closed contact 85, thereby opening the circuit of the supervisory signal AS to cause the efi acement of said signal AS. The operator observing the efiacement of said signal AS, will know that the subscriber at substation D has initiated another same as described above when used for call, and'willt-ake care of it in the same manner as herelnbetore described. The sub- "scriber at substation E may recall and signal the operator at cord (1' in the'same manner, by opcratlng l11S hand generator g to cause the energization of relay HR to bring about the etfacement of the supervisorysignal CL to indicate to the operator that the subscriber at substation E has'initiated a call and she will takecare of the call in the usualmanner, as pointed out in the foregoing specification.

The operatlon of my cord circuit C 1s the interconnecting a common battery telephone line, and a magneto telephone line, that is, either end of the cord C Wlll operate in the same manner when connected to a common F battery telephone line as described in the connected to a magneto line,- as set outabove in describing its connection with a magneto telephone line.

From the foregoing specification, it will' be clearly understood how the cord Got my invention will operate when used ior interconnecting a common battery telephone line, and a magneto telephone line, so that .a

description of the same is not deemed Having described a particular embodiall modifications and changes which may come within the spiritand scope of the apiended claims.

What I claim as new and desire tosecure 7 by United States Letters Patent, is:

1. In a telephone system including telephone lines, a link circuit for interconnecting the same, an operators telephone set normally disconnected from said link circuit, a manually operated key for connecting said telephone set to said link circuita'nd means for automatically disconnecting said telephone set from said linkcircuit, even though said key is operated, when said link circuit is connected to abusy telephone line or when the calling and called subscribers lines interconnected by said link circuit are in closed circuit. f

2. I11 a telephone system including telephone lines, a link circuit for interconnect ing the same, an operators telephone set, a manuallyioperated key for operatively connecting said operators telephone set to said link circuit, electromagnetic means for disconnecting said telephone set from said link circuit when said link circuit is connected to a busy line or when two subscribers of said lines are in conversational circuit through the medium of said link circuit, when said key is operated.

3. In a telephone system-including a calling and a called subscribers telephone line,

a link circuit for interconnecting said tele-' phone lines, an operators telephone set normally disconnected from said link clrcuit, a

key for connecting said telephone set to said link circuit, means for said link circuit for automatically disconnecting said telephone set from said link circuit when both the calling and called subscribers have their receiver's' removed from their respective swltchhooks and said key'is in its operated posi- V tlon, automatic rlnging means for said link circuit for signalling the called subscriber, and automatic means controlled by the callingsubscriber for automatically disconnecting ringing current from the called line prior to the response of the called subscriber. 4, In a telephone system including a callmg and a called subscribers telephone line, a

link circuit'for interconnecting said lines, an

operatorstelephone set, a manually operated keyfor connecting said telephone set to said link circuit V when only one subscriberon said telephone lines has his receiver removed from its switchhook, means. for automaticalr lyg disconnecting said telephone set from said link circuit when said link circuit is connected to a busy telephone line or When the calling and called subscribers lines are current from the called line prior to the.

scriber.

response of the called subscriber.

5. In a telephone system including calling and called subscribers telephone lines, a

plurality of cord circuits having manual connecting terminals at each oftheir ends .for interconnecting said lines, an operators telephone set for said cord clrcults but normally disconnected therefrom, a manually operated key for connecting said telephone setto any one of said cordcircuits when the I same is connected to 3 an idle subscribers' telephone lme, and automat c means for 'disconnecting said telephone set from said link circuit when "said link-circuit is connected to a busy line and the calling and called subscribers lines are in closed circuit and for preventing the connection of said telephone set to said cord circuit when the said cord circuit is connected to a busy subscribers telephone line and said key is operated.

6. In a telephone system including calling and called subscribers telephone lines appearing in multiple jacks before a plurality of operators positions, an individual groupof link circuits for each operators position having manual connection terminals for in terconnecting said calling and called telephone lines via said multiple jacks, an op erators telephone set for each group of link circuits and normally disconnected therefrom, a manually operated key for con necting said telephone set to any one of said link circuits to which said telephone set is individual, means for automatically disconnecting said telephone set from' said link circuit when said link circuit is connected to a busy telephone line or when the calling and called subscribers lines are in closed circuit, and electromagnetic means for preventing the connection of said telephone set to one of said link circuits when said one link circuit is connected to one ofsaid tele phone lines subsequently to the connection of another link circuit to said one telephone line and the key of said one link circuit is operated.v i i a,

7. In a telephone system including a 'call ing anda called telephone line, alink circuit for interconnecting said lines, an operators set for said link circuit but normally "dis-. connected therefrom, manually operated means for connecting said telephoneset to said link circuit, electromagnetic means, for preventingthe connection of said telephone set-to said link circuit when the calling and called subscribers have their receivers, 11emoved from their respective switchhooks, said last means inoperative when one of said subscribers has replaced his receiver upon its switchhook, automatic -means for said 'link circuit for signalling the called subscriber, and automatic means controlled by the calling subscriber for automatically disconnecting ringing current from the called line prior to the response of the called sub- '8. In ateleplione system including a calling telephone'line anda called telephone line, a link circuitfor interconnecting said lines, supervisory signals for said link circuit, electromagnetic means including a pair of relays for providing secret service in said link circuit When interconnectingthe calling and called subscribers lines andboth have ing subscriber for automatically disco'nnecting ringing current from the called line prior to the response of the called subscriber. V

9. In a telephone system including comtelephone lines, a link circuit for intercontheir receivers removed from their respec- I tive switchhooks, sald means controlledover m necting any two of said lines, an operators telephone set for said link circuit but normally disconnected therefrom, manual means for connecting said telephone set to said- 9 link circuit, electromagnetic means for said j link circuit for preventing the connection of said telephone set to said link circuit when said link circuit is connected to a busy common battery line or when thecalling and called subscribers on common battery lines interconnected by said link circuit have their receivers removed'from their switchhooks, supervisory signals for said link cir' cuits, said electromagnetic means operable called sub- 10,5,- 1

mon battery telephone lines and magneto 115 'j 'OVQ1KD1ag11Bt0 lines when said link circuit is- ,"connected to a magneto line, to effect the operation of saidv signals to signal for disconnection or to signalfor a recall.

10. In a telephone system including common battery telephone lines and 'ma'gneto @"tQlQPhOIIG- HIIGS', a link circuit for interconv nectingsaid telephone lines, an operators telephone set, electromagnetic means for said-link circuit for preventing the operator from listening 111011 a conversation through said telephone-set and link circuit when said l nk circuit is connected to a busy common battery telephone line or when said link circuit is interconnecting two common battery telephone lines, and the subscribers on these lines have their receivers removed from 'their switchhooks, and supervisory signals for said link circuits, said electromagnetic.

means controlled over said magneto telephone lines, when said link circuit is con- 'nectedfto said magneto lines, to efiect the operationof' said signals to signal for dis connection or to signal for a recall.

' 11. In a telephone system including common battery telephone lines and magneto telephone lines, a link circuit for interconnecting any two of said telephone lines, a pair of rela'ys operable to, provide secret service'on said link circuit'iwhen connected common battery lines and the subscribers thereon 'have their receivers disengaging,

their switchliooks, and supervisory signals for said link circuit, said pair of relays concircuit is connected to magneto lines to effect operation of said signals to signal for disconnection or for a recall.

12. In a telephone system including telephone lines of different character, linkcircuits for interconnecting. said telephone lines, supervisory signals for said link circuits, automatic means including a pair of relays for each of said link circuits for providing secret service on said link circuits when connected to busy telephone lines'of one class or when interconnecting telephone lines of said one class and both thefcalling and called subscribers" thereon have their re- 'ceivers removed from their respectiveswit-ch hooks, said pair of relays operable: when the link circuits are connected to telephone lines of a different class to effect operation ,of said signals to signal fordisconneet-ion or to signal for a recall.

13. In a telephone system including telephone lines of different classes, a link circuit for interconnecting any two of said telephone lines, a pair of relays bridged across the talking conductorsof said link circuit,

another relay forv said link circuitcontrolled by said pair of relays for providing secret service on said link circuit when said link circuit is connected to telephone lines of one class and supervisory signals for said link circuit, saidpair of; relays operable to effect operation of said signals to signal for idisconnection or recall when'said link circuit is connectedtotelephone lines of another class. V

Signed by ine at Chicago, in the county of'Cook and State of Illinois, this 27th day of December, 1922. trolled over magneto lines when said link BERT A. WALLACEJ' 

